1. Field of the Invention
The present invention relates generally to a wireless communication system, and in particular, to a method and system for indicating uplink/downlink data burst allocation in a wireless communication system.
2. Description of the Related Art
Active research on the 4th Generation (4G) communication system, which is the next generation communication system, is being conducted to provide users with services guaranteeing various Qualities-of-Service (QoS) at a data rate of about 100 Mbps. In particular, active research on the 4G communication system is being carried out to support a high-speed service that guarantees mobility and QoS for Broadband Wireless Access (BWA) communication systems such as a wireless Local Area Network (LAN) system and a wireless Metropolitan Area Network (MAN) system. An Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system is a typical BWA communication system.
The IEEE 802.16 communication system is specified as a BWA communication system employing an Orthogonal Frequency Division Multiplexing (OFDM) scheme and/or an Orthogonal Frequency Division Multiple Access (OFDMA) scheme. Compared with the conventional wireless technology for a voice service, the IEEE 802.16 communication system can transmit more data for a short time because of its wide bandwidth for data, and allow all users to share channels, increasing channel efficiency. In the IEEE 802.16 communication system, because all users connected to a base station (BS) share common channels, and a period for which each user uses the channel is allocated thereto by the BS for every uplink/downlink frame, the BS must provide uplink/downlink access information every frame so that the users can share the channels. Messages used for providing the uplink/downlink access information are called uplink/downlink (UL/DL) MAP messages.
A Hybrid Automatic Repeat reQuest (H-ARQ) MAP message is one of the MAP messages. The H-ARQ MAP message is used for supporting a mobile station (MS) that can use an H-ARQ scheme. For example, upon receiving the H-ARQ MAP message from a BS, an MS analyzes the received H-ARQ MAP message. A MAP information element (IE) included in the H-ARQ MAP message is called a Compact UL/DL MAP IE, and the MS can receive/transmit data bursts according to information in the Compact UL/DL MAP IE.
FIG. 1 is a diagram illustrating a frame structure used in a conventional wireless communication system. Referring to FIG. 1, the frame can be divided into an uplink (UL) subframe region and a downlink (DL) subframe region. The DL subframe region includes a period in which a preamble is transmitted, a MAP period, and a burst period in which DL data bursts are allocated. The UL subframe region includes a UL control period and a burst period in which UL data bursts are allocated.
The UL/DL data bursts are sequentially allocated in units of subchannels on the vertical axis for a unit symbol period (i.e., 1-symbol period) on the horizontal axis, and when the allocation of the data bursts to all subchannels for one symbol period is completed, the UL/DL data bursts are sequentially allocated again in units of subchannels for the next symbol period.
In FIG. 1, data bursts #1, #2 and #3 are data bursts allocated in a particular symbol period #n. For example, the BS allocates a subchannel #0 through a subchannel #5 for the data burst #1, and after completion of the subchannel allocation, allocates a subchannel #6 through a subchannel #8 for the next data burst #2. Thereafter, the BS allocates a subchannel #9 through a subchannel #10 for the next data burst #3, completing the subchannel allocation for the symbol period #n.
After completion of allocating the subchannels for the data bursts in the symbol period #n, the BS sequentially occupies again subchannels for data bursts #4 and #5 in the next symbol period #(n+1), completing the subchannel allocation for the symbol period #(n+1). Such a data burst allocation method is called “1-dimensional data burst allocation.”
If a particular BS and its adjacent BS use the same subchannel band, the particular BS may receive an interference signal from the adjacent BS, causing a loss of data bursts. The data burst loss leads to a reduction in data transmission efficiency.
In order to solve this problem, a 2-dimensional burst allocation (shown by bold lines in FIG. 2) method has been proposed. However, there is no proposed scheme for supporting various operation modes and Modulation and Coding Schemes (MCSs) between a BS and an MS. For example, because the BS uses an error-robust MCS for all MAP messages, it must use the error-robust MCS even for the MAP message for an MS in a good channel state, causing a reduction in transmission efficiency.